Simultaneous preparation of TiO2 and ammonium alum,and microporous SiO2 during the mineral carbonation of titanium-bearing blast furnace slag

In this study,a route for simultaneous mineralization of CO2 and production of titanium dioxide and ammonium alum,and microporous silicon dioxide from titanium-bearing blast furnace slag(TBBF slag)was proposed,which is comprised of(NH4)2 S04 roasting,acid leaching,ammonium alum crystallization,silicic acid flocculation and Ti hydrolysis.The effects of relevant process parameters were systematically investigated.The re sults showed that under the optimal roasting and leaching conditions about 85%of titanium and 84.6%of aluminum could be extracted while only 30%of silicon entered the leachate.84%of Al^3+was crystallized from the leachate in the form of ammonium aluminum sulfate dodecahydrate with a purity up to 99.5 wt%.About 85%of the soluble silicic acid was flocculated with the aid of secondary alcohol polyoxyethylene ether 9(AEO-9)to yield a microporous SiO2 material(97.4 wt%)from the crystallized mother liquor.The Al-and Si-depleted solution was then hydrolyzed to generate a titanium dioxide(99.1 wt%)with uniform particle size distribution.It was figured out that approximately 146 kg TiO2 could be produced from 1000 kg of TBBF slag.Therefore,the improved process is a promising method for industrial application.

Recent progress of efficient utilization of titanium-bearing blast furnace slag

Titanium-bearing blast furnace slag(BFS)has valuable compositions and potential environmental hazardousness.Thus,developing efficient and green approaches to utilize BFS is highly desired for resource economization and environmental protection.In the past decades,many attempts have been adopted to reuse BFS efficiently,and significant advances in understanding the fundamental features and the development of efficient approaches have been achieved.This review provides a comprehensive overview of the latest progress on the efficient utilization of BFS and discusses the mechanism and characteristics of various approaches,along with their application prospects.In particular,the extraction and enrichment of titanium-bearing phases from BFS are highlighted because of the high availability of titanium resources.This systemic and comprehensive review may benefit the design of new and green utilization routes with high efficiency and low cost.

Indirect mineral carbonation of titanium-bearing blast furnace slag coupled with recovery of TiO_2 and Al_2O_3

Large quantities of CO2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO2 emission reduction and comprehensive utilization of the solid waste. This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace （TBBF） slag, in which the TBBF slag is roasted with recyclable （NH4）2SO4 （AS） at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH3 produced during the roasting is used to capture CO2 from flue gases. The NH4HCO3 and （NH4）2CO3 thus obtained are used to carbonate the CaSO4-containing leaching residue and MgSO4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium, magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2：1 and 350℃ for 2 h. The leaching solution was subjected to hydrolysis at 102℃ for 4 h with a Ti hydrolysis ratio of 95.7%and the purity of TiO2 in the calcined hydrolysate reached 98 wt%. 99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH3. The carbonation products of Ca and Mg were CaCO3 and （NH4）2Mg（CO3）2·4H2O, respectively. The latter can be decomposed into MgCO3 at 100-200℃ with simultaneous recovery of the NH3 for reuse. In this process, approximately 82.1% of Ca and 84.2% of Mg in the TBBF slag were transformed into stable carbonates and the total CO2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium, cement and light magnesium carbonate production for the replacement of natural resources.

Antibacterial Properties of V-doped Titanium-bearing Blast Furnace Slag Prepared at Different Calcination Temperatures

Perovskite-type V-doped titanium-bearing blast furnace slag (VTBBFS) photocatalyst was prepared by high-temperature solid phase method.The influence of calcination temperature on the photocatalytic and antibacterial properties of VTBBFS was studied in details.Its composition and microstructure were evaluated by X-ray diffractometer,ultraviolet-visible absorption spectrometer,Fourier transform infrared spectrometer and scanning electron microscope.The antibacterial properties of VTBBFS to Candida albicans were investigated by flask oscillation method.The results showed that the optical absorption and antibacterial properties of VTBBFS were the best with 10%(ω) doping of vanadium,prepared at 800℃ for 2 h,and its sterilization rate was close to 100% to Candida albicans (ATCC10231).The minimum inhibitory and minimum bactericidal concentrations were 25 and 50 mg/mL.When the concentration was 0.2 μg/mL,the catalyst had the least toxic toxicity.

Preparation of UV-visible light responsive photocatalyst from titania-bearing blast furnace slag modified with(NH_4)_2SO_4

Sulfate-modified titanium dioxide-bearing blast furnace slag（STBBFS） photocatalysts were prepared by the high energy ball milling method with（NH4）2SO4 and titanium dioxide-bearing blast furnace slag（TBBFS） as raw materials.X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,thermogravimetric analysis（TGA）,UV-visible diffuse reflectance absorption spectra（UV-Vis）,adsorption experiment and photocatalytic degradation measurement were conducted to characterize the structure,surface status,light absorption capacity,adsorption capacity and photocatalytic activity of the obtained photocatalysts.The adsorption equilibrium was described by the Langmuir isotherm model with a maximum adsorption capacity of 8.25 mg/g of Cr（VI） ions onto the STBBFS photocatalysts.As a result,sulfation of TBBFS improved the photocatalytic activities of STBBFSx photocatalysts.At a low calcination temperature,the photocatalytic activity of STBBFS300 photocatalyst was markedly higher compared with TBBFSx prepared at high calcination temperature,indicating that the photocatalytic activity of STBBFSx photocatalyst was determined by the balanced result between adsorption capacity and perovskite content.

Synthesis of (Ca, Mg)-α′-Sialon-AlN-BN powders from boron-rich blast furnace slag by microwave carbothermal reduction-nitridation

(Ca, Mg)-α′-Sialon-AlN-BN powders were synthesized by the carbothermal reduction and nitridation (CRN) method using boron-rich slag, one of the intermediate products from pyrometallurgy separation of pageit, as the staring material. The influences of synthesis temperature and holding time on the phase composition and microstructure during the microwave CRN were studied by XRD, SEM and EDS. The comparison between two heating techniques, conventional and microwave heating, on the synthesized powder was presented as well. The experimental results revealed that the phase compositions and microstructures of the synthesized products were greatly affected by the synthesis temperature and holding time. With an increase in the synthesis temperature or holding time, the relative amount of α′-Sialon increased and α′-Sialon became the main crystalline phase at 1400 °C for 6 h. The synthesized products also contained AlN, BN and a small amount of β-SiC. Elongated α′-Sialon grains, short rod AlN grains, aggregate nanoscale BN grains were observed in the synthesized powders. The reaction temperature of microwave heating method was reduced by 80 °C, the reaction time was shortened by 2 h, and more elongated α′-Sialon grains with large aspect ratio were observed.

Dripping and evolution behavior of primary slag bearing TiO2 through the coke packed bed in a blast-furnace hearth

To investigate the flow of primary slag bearing TiO2 in the cohesive zone of blast furnaces, experiments were carded out based on the laboratory-scale packed bed systems. It is concluded that the initial temperature of slag dripping increases with decreasing FeO content and increasing TiO2 content. The slag holdup decreases when the FeO content is in the range of 5wt%-10wt%, whereas it increases when the FeO content exceeds 10wt% . Meanwhile, the slag holdup decreases when the TiO2 content increases from 5wt% to 10wt% but increases when the TiO2 content exceeds 10wt%. Moreover, slag/coke interface analysis shows that the reaction between FeO and TiO2 occurs be- tween the slag and the coke. The slag/coke interface is divided into three layers： slag layer, iron-rich layer, and coke layer. TiO2 in the slag is reduced by carbon, and the generated Ti diffuses into iron.

Effects of additives on the phase transformation, occurrence state, and the interface of the Ti component in Ti-bearing blast furnace slag

The influences of additives on the phase transformation, occurrence state, and the interface of the Ti component in Ti-bearing blast furnace slag were investigated. After oxidation, most of the Ti component in the slag was enriched into the perovskite phase, which served as the Ti-rich phase during the crystallization process. The phase transformation, occurrence state, and the interface of the Ti component were observed to be affected by the addition of different types of agents. During the oxidation process, titanaugite and Ti-rich diopside phases gradually transformed into non-Ti phases（anorthite： CaMgSi2O6 and CaAl2Si2O8） in the form of dendrites or columns, which were observed to be distributed at the surface of the perovskite phase. Several more cracks appeared along the grain boundaries of the perovskite phase after the addition of P2O5, facilitating the liberation of the perovskite phase. Composite additives combining both an acid and a base, such as CaO ＋ CaF2 or P2O5 ＋ CaF2, were used. We observed that the disadvantages of using single additives were successfully overcome.

Effects of MgO and TiO_2 on the viscous behaviors and phase compositions of titanium-bearing slag

The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.

Titanium Transfer in Slag/Metal Systems for Ironmaking

The smelting of titaniferous magnetite in blast fuynace in China is unique in the nature of problems and their solutions. Fundamentals of this successful technology will be discussed. Topics to be covered are: (1) the characteristics of high content TiO_2 in blast furnace slag; (2) influence of various factors on Ti transfer process; (3) raising oxygen potential for adequate fluidity of the slag with TiO_2 in the range of 25-30 wt-% and stability of TiC and TiN in slag.

基于PSO-GRNN的含钛高炉渣活化焙烧浸出成分预测模型

活化焙烧是一种回收利用含钛高炉渣中钛资源的新方法。为通过反应条件快速获得回收渣中成分含量,建立了基于粒子群优化的广义回归神经网络(PSO-GRNN)预测模型。借助斯皮尔曼(Spearman)相关性分析筛选特征变量作为模型输入,利用PSO优化GRNN神经网络的权重与节点阈值,通过与偏最小二乘回归(PLS)、随机森林(RF)以及支持向量回归(SVR)算法的对比,确定了提出模型的优势。研究结果表明,PSO-GRNN具有最小的RMSE和最大的R2,表明在该数据集上所设计的PSO-GRNN有最佳的模型性能,可以为后续实验或工业应用提供一定的指导。

熔融制样-X射线荧光光谱法测定氯化炉渣中12种组分含量

本文采用钒钛高炉渣、钒渣、高钛渣、高炉渣等标准样品建立含量范围梯度大的标准曲线,同时测定氯化炉渣中Al、Si、Fe、Ca、Mg、P、Ti、Mn、K、Na、V、Cr。采用熔融制样,以四硼酸锂-偏硼酸锂混合熔剂(67∶33)作为熔样体系,讨论了熔融制样熔剂选择、熔片温度、稀释比及脱模剂用量等条件对熔片效果的影响。使用变化理论α系数校正,谱线重叠校正对标准曲线进行校正,对方法的精密度进行了考察,其中相对标准偏差为0.21%~4.20%(n=10)。分析结果与容量法和电感耦合等离子体原子发射光谱法分析结果进行对比,结果令人满意,本方法可适用于氯化炉渣样品成分的快速分析。

含钛高炉渣还原提取钛硅合金后尾渣制备钙长石-尖晶石轻质多孔材料研究

以含钛高炉渣提取硅钛合金后的尾渣为主要原料,采用发泡法制备了钙长石-尖晶石质轻质多孔材料。研究了尾渣的物相组成,尾渣和朔州土及石英加入量、发泡剂、促凝剂、稳定剂、煅烧温度等工艺参数对材料物相组成、气孔率、体积密度以及孔径分布等性能的影响。结果表明:提取硅钛合金后尾渣的主要物相为铝酸一钙(CA)、二铝酸一钙(CA_2)、镁铝尖晶石(MA)以及少量钙铝黄长石(C_2AS);多孔轻质材料的主晶相为钙长石,含有少量镁铝尖晶石;多孔轻质材料的显气孔率可以稳定控制在75%左右,体积密度控制在0.35～0.85 g/cm3之间;适宜的烧成制度为1300℃×3 h。

工艺参数对含钛高炉渣合成(Ca,Mg)α′-Sialon-AlN-TiN粉的影响

以含钛高炉渣、硅灰、高铝矾土熟料和炭黑为原料,采用碳热还原氮化法合成了(Ca,Mg)α′2Sialon2AlN2TiN粉。用X射线衍射法测定了产物相组成及相对含量,研究了合成温度和恒温时间对反应过程的影响,并对合成机理进行了探讨。结果表明:合成温度对(Ca,Mg)α′2Sialon2AlN2TiN粉的合成过程影响显著,随着合成温度升高,产物中α′2Sialon相含量增大,1480℃时α′2Sialon含量达最大,是最佳的合成温度。恒温时间对产物相组成的影响不十分显著,但较长的恒温时间可使还原氮化反应进行得更充分,恒温8h的试样中α′2Sialon含量最高,是较理想的恒温时间。合成过程中SiO的挥发导致试样较大的质量损失,且随着合成温度升高和恒温时间延长而增大。

Cr(VI)-乙酸复合体系中硫酸盐掺杂的含钛高炉渣光催化还原Cr(VI)

采用煅烧的硫酸盐掺杂的含钛高炉渣作光催化剂,研究了Cr(VI)-乙酸(AA)复合体系中Cr(VI)的光催化还原效率,考察了初始pH值、Cr(VI)初始浓度、AA/Cr(VI)体积比、协同效率因子、光催化剂使用寿命等因素的影响.结果表明,增大AA/Cr(VI)比到0.2%,Cr(VI)的还原效率先增大到27.55%随后逐渐降低.酸性条件下,Cr(VI)单一体系和Cr(VI)-AA复合体系中Cr(VI)的还原率和吸附率都明显提高;相同反应时间下(110min),初始pH1.5时,2种体系中Cr(VI)的还原效率分别为76.32%(单一体系)和100%(复合体系).复合体系中协同效率因子始终大于0.循环使用5次后催化剂对Cr(VI)的光催化还原率为92.2%.Cr(VI)在Cr(VI)-AA体系中的光催化还原遵循Langmuir-Hinshelwood动力学规律.

含钛高炉渣合成(Ca,Mg)α′-Sialon-AlN-TiN粉末

在热力学分析的基础上 ,以含钛高炉渣为主要原料 ,采用碳热还原氮化法合成了 (Ca,Mg)α′ Sialon AlN TiN粉。确定了合成过程的最佳工艺参数 :反应温度 14 80℃ ,保温 10h,配碳量为理论值的 1.5倍 ,氮气流量 4 0 0mL/min。采用X射线衍射仪和扫描电镜研究了合成产物的相组成和显微结构。结果表明 :产物中除有主要物相α′ Sialon、AlN和TiN外 ,还有少量 β SiC ,15R和 β CaSiO3 等杂质相。其中 ,(Ca,Mg)α′ Sialon多以片状而AlN多以球形或短柱状形式存在。EDS分析结果表明 ,Ca2 + 、Mg2 + 都进入了α′ Sialon晶格中 ,但Ca2 + 的固溶量远高于Mg2 + 。

ICP-AES测定钒钛高炉渣中的MnO、P、V_2O_5、TiO_2

采用电感耦合等离子体原子发射光谱法（ICP-AES法）测定钒钛高炉渣中MnO、P、V2O5、TiO2的含量,利用盐酸、硝酸、氢氟酸、高氯酸溶解钒钛高炉渣,优选适宜的仪器测定参数和最佳分析谱线,共存元素间的干扰采用谱线背景扣除的方法予以消除。实验结果表明,钒钛高炉渣中的MnO、P、V2O5、TiO2在一定浓度范围内具有良好的线性关系,相关系数在0.999以上,测定结果的相对标准偏差在0.45%~5.10%之间,加标回收率在96%~107%之间。

Cr(Ⅵ)-柠檬酸-硝酸铁复合体系中光催化还原Cr(Ⅵ)

利用高能球磨法制备了钙钛矿型硫酸盐掺杂的含钛高炉渣光催化剂,考察了初始pH值对Cr(Ⅵ)-柠檬酸-硝酸铁(Cr(Ⅵ)-CA-FN)复合体系中Cr(Ⅵ)吸附效率和光催化还原效率的影响,并探讨了Cr(Ⅵ)-CA-FN复合体系中Cr(Ⅵ)可能的光催化还原机理。结果表明:在Cr(Ⅵ)-CA-FN复合体系中,酸性条件下有利于Cr(Ⅵ)的光催化还原,最佳pH值为2.5;柠檬酸和Fe(Ⅲ)降低了吸附对Cr(Ⅵ)还原率的影响,有效地抑制电子-空穴对的复合,促进光生电子还原Cr(Ⅵ)离子;六价铬浓度的降低一部分是光催化还原所致,另一部分是由于催化剂本身含有的二价锰离子还原所致。

高炉软熔带渣对原位TiN/O′-sialon材料侵蚀的研究

采用静态熔滴法研究了模拟高炉软熔带渣对原位TiN/O′sialon材料的侵蚀机制。利用高温X射线透视装置观察炉渣的熔化和与材料的相互作用过程。XRD分析残渣中的物相 ,EPM分析材料被侵蚀部位的显微结构和元素分布。结果表明 :熔渣对材料的侵蚀主要是熔渣渗透并与材料发生化学反应。材料被侵蚀后结构发生变化 ,可大致分为渣带、渗透带和未变带。熔渣与材料相互作用生成的新的高熔点相以及熔入的TiN使熔渣的粘度增大、流动性降低 ,进而阻止熔渣的进一步侵入。材料中TiN含量的增加将提高材料的抗渣侵蚀能力。

水泥-矿渣体系两类C-S-H凝胶体积分数的定量计算

水泥-矿渣二元体系水化产物体积分数的定量计算是理论预测其微结构发展的重要基础。根据水泥-矿渣水化反应特征,文中给出了详细的计算表达式;采用热重-差示扫描量热(TGDSC)综合分析手段来验证所提表达式的合理性,并根据Jennigs-Tennis模型(简称J-T模型),给出了低密度和高密度C-S-H凝胶体积分数的定量计算公式,对水泥-矿渣二元体系中两种凝胶的相对量进行定量计算。结果表明:水泥-矿渣二元体系中矿渣完全水化的最佳掺量为54.4%,两种凝胶的相对量随矿渣掺量的增加而增加。